1. Field of the Invention
The present invention is related to a passive repeating plyometric muscle strengthening method and an apparatus for the method, and especially to a method and an apparatus for training a person by continuous bearing of passive exercising load, it is a plyometric and eccentric contraction muscle training in a short time with a large amount of acting units.
2. Description of the Prior Art
Muscle training must progresses gradually; in training muscles of the whole body of a man, we must try to continuously increase the times and load to continuously increase the maximum muscle strength and muscle durability. In a plyometric or rebounding action, there must be a muscle contraction; if an external force (load) is larger than the active resistive capability of the muscle, the muscle is forced to stretch, or when in need by an action, the muscle may actively contract from stretching under some load, these are both called eccentric contraction. And another term “concentric contraction” means that the muscle is shortened when in contraction, thereby limbs will move toward the direction of contraction of the muscle. Almost all the movement actions are completed under interaction of the eccentric contraction and the concentric contraction. When in an eccentric contraction, the muscle is stretched like an elastic body; by elongation of the series elastic components (SEC), strength is generated. The general strength generated can be the sum of the contractile components (CC) and the series elastic components (SEC) (referring to FIG. 1). Such mechanical action increases the induced concentric contraction accompanying with the series elastic components generated. When a larger elongation and contraction action is done, there are a few cross-bridges stretched along therewith in a state of keeping in combination with actin. A faster elongation and eccentric contraction period can store larger mechanic energy source. The combination of the eccentric contraction and the concentric contraction is generally called stretch-shortening cycle. This process will generate larger strength and power output at the last action (concentric contraction) thereof than the pure concentric contraction. Muscle is stretched in advance and then is fast contracted. A scholar Chu (1992) divided the process into the eccentric-phase and the contraction-phase; the former indicates fast stretching of muscle fibers before contraction; while the latter indicates the muscle contraction itself. Chu called the short period between the two phases amortization phase. In addition to this, Verkhoshanski divided the process into the yield phase and the overcoming phase; the former indicates forced stretching of muscle; while the latter indicates the reactive fast muscle contraction. During the eccentric contraction period, load is transformed into the SEC and is stored as an elastic energy source, the concentric contraction thereafter can obtain the elastic energy source stored in the SEC and is used for contraction.
Plyometric muscle training takes advantage of forceful muscle contraction by the elements of elongation, elasticity and contraction of which the elongation is elongated through skeleton, the elasticity is stored to generate force for contraction later for training (Lundin, 1985). The eccentric and concentric contraction style training mode has larger strength and power than the pure concentric contraction style training. The plyometric muscle training is necessary for obtaining good neurotic muscle reflex, stretching reflex, eruptive power and jumping action, especially for obtaining large acting units within a very short time period.
Generally, in using conventional training appliances (such as bar bells or normal muscle training instruments) for training, the appliances are mostly fixed, and exercising is repeated for many times. That is, the appliances themselves are fixed; they are moved or erected by trainees. However, if repeating times by a trainee are few, and speed of action is slow, increasing of strength of muscle must be little. For a normal steady contraction of constant length with slow speed, calling up of acting units is done in a way from slow to fast speed. When in an extremely fast action, the acting units of the slow-twitch muscles will be inhibited, and only the acting units of the fast-twitch muscles are called up. For example, the acting units to act fast with high threshold have the priority to call up when they are in the phase of fast concentric contraction and eccentric or reduced fast muscle action. In the training action modes of the strength of muscles of the lower limbs for the Cheng's passive repeating plyometric muscle strengthening apparatus, the articulates of the lower limbs are moved in the mode of stretching and contracting with high speed. During the action period, the trainees are requested to do their best to step pedals. When it is in the lifting stage of the pedals, the musculus quadriceps femoris, the Achilles tendon and the musculus gastrocnemius are in the full power high-speed eccentric contraction phase. This connects serially with the concentric contraction following immediately to form a stretch-shortening cycle (SSC) of high speed and high strength. When the muscles are stretched to elongate, the fibers of the musculus fusiformis internus in the muscular tissue is simultaneously stretched to elongate to induce reflective muscle contraction. The contractile components (CC) in the muscles and the stored series elastic components (SEC) induced by stretching will generate larger and faster strength. Before muscle contraction, a fast muscle stretching may generate an even larger contraction. While a faster contraction speed can be obtained after muscle stretching (eccentric), having larger and faster concentric strength and power output. And more, the plyometric muscle training increases the threshold of the Golig tendon organ (GTO) and thus increases the threshold of the muscle tendon to increase the load in elongation of muscle. A higher elongation of muscle can resist larger load in elongation to generate stronger elongation reflex.
And more, if a trainee uses a conventional muscle training method, regardless it is for stretching a knee or an elbow, to complete an action, it needs at fastest 0.5˜1.0 second, while a violent sporting competition, such as 100 m race, requires only 0.2˜0.3 second for stretching a knee. And in an action of skiing down a slope, it needs faster speed (down to several milliseconds for stretching a knee. Thereby, only the passive muscle training with high frequency can render the muscle and neurotic systems to reach the practical conditions approximate to that of a sporting competition.